The purpose of this project is to perfect a method for using tissue culture grown skin epithelial cells as autografts. By using sterile dead pigskin as a substrate, extensive sheets of human epithelium can be selectively propagated. These cells differentiate to form the four layers typical of skin epithelium in vivo. The cells are considered epithelial because of their morphology, possession of desmosomes (intercellalar bridges) and tonofibrils, and because they form maturating epithelium in vitro and upon autografting. Current work involves the development of a quantitative assay to measure epithelial cell growth by protein or DNA synthesis. Using this assay we will determine the growth stimulating or inhibiting properties for a number of chemical agents ranging from fat soluble vitamins to antiseptic agents and antibiotics used for topical application. The agents will also be tested for their enhancement or inhibition of the cell maturation process, a function that is eventually lost with physical subdivision of the cultures.